border-1px($color)
  position:relative
  &:after
    display: block
    position: absolute
    left:0
    bottom:0
    width: 100%
    border-bottom:1px solid $color
    content:''

border-none()
  &:after
    display:none

// bg-image($url)
//   background-image: url($url + "@2x.png")
//   @media (-webkit-min-device-pixel-ratio:3),(min-device-pixel-ratio:3)
//     background-image: url($url + "@3x.png")